1. Field of the Invention
The present invention relates to recording devices and recording control methods, and particularly relates to a recording device and a recording control method for recording by ejecting ink from, for example, an inkjet recording head onto a recording medium.
2. Description of the Related Art
As information processing devices such as copiers, word processors, and computers and communication equipment become widely available, digital image recording devices for such devices are rapidly becoming widespread, including those having an inkjet recording head (hereinafter referred to as a recording head). Recording heads used for such recording devices have densely arranged ink outlets and ink channels serving as a recording element array composed of densely arranged recording elements to achieve higher recording speeds. Typical recording heads have a plurality of recording element arrays to provide color recording.
Recently, there has been an increasing demand for higher-quality image recording using recording devices both in a normal recording mode in which line images such as characters are recorded on recording media such as plain paper and in a photo-quality mode in which natural images are recorded with high image quality on recording media such as glossy paper.
The ink properties required differ between glossy paper, which has a coating layer, and other recording media such as plain paper, which has less absorbency and color development properties. For example, important factors for glossy paper include glossiness, graininess, and chroma while those for plain paper include density and absorption speed.
Different types of inks are used for recording according to the properties of recording media and the image quality for recording. For black inks, particularly, different types of inks are preferably used for different types of images for recording. For glossy paper, for example, a photo black ink is preferred for its low image graininess and excellent glossiness for mixed colors. For plain paper, on the other hand, a matte black ink is preferred for its excellent color development properties. Japanese Patent Laid-Open No. 2004-155831 (corresponding to U.S. patent application Ser. No. 2005-041082) discloses a recording system capable of utilizing the two types of inks.
Thus, the use of appropriate inks according to the type of recording media is a general method for supporting recording media with different properties. Indiscriminately increasing the number of inks used, however, results in bulky recording heads with an increased number of recording element arrays corresponding to the individual inks. Recording devices having such recording heads are bulky and often contribute to increased cost.
Japanese Patent Laid-Open No. 2004-136507 discloses a recording device capable of interchanging ink sets according to the properties of recording media and user demands.
This device allows the interchangeable use of, for example, an ink set suitable for high-speed recording and another ink set suitable for photo-quality mode.
The above known systems, however, leave the problems described below:
For the interchangeable use of different types of inks for the same recording element array, the inks are difficult to completely interchange; a residue of the ink used before the interchange may be mixed in the ink used after the interchange in a recording head and ink supply channels. If the content of the residual ink is low, the mixed ink is often similar in image quality to the ink used after the interchange. The mixed ink, however, can be unstable in terms of ejection properties and reliability. If, particularly, the inks used before and after the interchange are pigment inks, the dispersants used for pigment dispersion often deteriorate, leading to degraded dispersibility. As a result, the pigment particles aggregate and obstruct the control of recording elements. This results in unstable ink ejection.
The mixed ink can be completely replaced with the ink used after the interchange by draining the ink remaining in the recording head and the ink supply channels using a built-in recovery mechanism or by ejecting and consuming the residual ink in a non-recording region in the recording device. Completely draining the ink remaining in the recording head and the ink supply channels, however, increases the amount of ink consumed in each interchange operation and thus raises operating cost. Complete draining after the interchange operation is also disadvantageous because it makes it difficult to reduce the time required for ink interchange.